1. Field of the Invention
The present invention relates to a printer for printing on single paper such as a slip, more specifically to an improvement of an adjusting means for a head gap which is provided in a given distance between a platen and a printing head and a securing means of the head gap adjusting means for maintaining the head gap.
2. Description of the Prior Art
Slip printers for printing on slip paper are conventionally constructed such that slip paper inserted through a side portion or a front portion of the printer is received by a printing device, and the printing device performs printing operation. The printing device is equipped with a platen and a printing head which is disposed above and opposing the platen. Slip paper is inserted into a given opening, namely a head gap provided between the platen and the printing head. The printing head performs printing on the slip paper supported on the platen. In order to obtain stable printed images, distance of the head gap must be uniform over the entire width of the platen. Therefore, the manufacturer normally adjusts head gaps before shipment of printers.
As a structure for adjusting head gap, for example, Japanese Unexamined Utility Model Publication (Kokai) No. 61-35846 discloses a structure, in which a platen can be moved up and down by rotating screws screwed on both ends of the platen. The screws can be rotated by operation from above, and after completion of the adjustment; the platen is secured by tightening securing screws, which penetrate a frame from the side thereof. Furthermore, Japanese Unexamined Utility Model Publication (Kokai) No. 1-76247 discloses a structure installed with an adjusting roller. The adjusting roller has a spiral inclined portion on its peripheral portion. The spiral inclined portion is inserted into a slit-shaped aperture formed on the both ends of a platen so as to move the platen up and down by virtue of the inclined portion when the adjusting roller is rotated. In this case, a plurality of claw portions formed on the outer surface of the adjusting roller engage with a securing claw portion so as to restrict rotation of the adjusting roller, whereby the adjusted position of the platen is fixed.